Pyrolytic carbon can be produced by conventional chemical vapor deposition processes to form a variety of carbon microstructures. This process has been used to produce nuclear fuel encapsulation pellets, highly oriented pyrolytic graphite, high purity pyrolytic protective coatings on graphite objects, pyrolytic carbon matrix in fiber reinforced composites, pyrolytic coatings on prostheses, and as interface layers between ceramic fibers and ceramic matrix in ceramic composites.
These processes have usually been found to be expensive and time consuming and, therefore, used as a value-added process to enhance the properties of the bulk material under development. The use of pyrolytic carbon as a bulk material for making other materials, such as filled rubbers, filled plastics, carbided metals, electrode structures, reinforcements, and in general any use which is common for other granular forms of carbon such as granular pitch, graphite powders, mesophase powders, carbon nanofibers, milled carbon fibers, granular activated carbons, and carbon blacks is severely restricted, because there has been no viable method for a low cost and high volume production of the pyrocarbon in a pure and finely divided form. As a result, some of the intrinsic properties of the material, which could be useful as a bulk material or raw material for other manufacturing steps, have not been exploited.
It is known in the art that pyrolytic carbon can be coated onto other objects for the enhancement of their qualities. U.S. Pat. No. 5,552,220, for example, teaches that specific carbon structures can be formed between the fibers in a matrix to create a composite material.
U.S. Pat. No. 4,796,701 teaches that a pyrolytic carbon coating on gravel can be used for drilling bed packings, and can enhance the packing efficiency of the gravel.
U.S. Pat. No. 3,977,896 teaches that objects can be suspended within a fluidized bed within a reactor designed to deposit a pyrolytic carbon coating on the objects of interest.
All of these references disclose that the process is viable when some high added value to the object or material is produced with a relatively small addition of the pyrolytic carbon material. This is primarily due to the fact that since the thickness deposition rate of the pyrocarbon deposition is quite small, only relatively small quantities of the pyrolytic carbon can be produced in an economical manner.
U.S. Pat. No. 4,013,760 teaches that large granular carbon materials with sizes greater than 100 microns can be coated with pyrolytic carbon and then milled or ground to create a finer granular material containing some pure pyrolytic carbon mixed with the original granular carbon.
Despite the above teachings of the prior art, none of the references provide a means of producing large quantities of substantially pure pyrolytic carbon directly in a very fine granular form.